Reference current loop

Abstract

Reference current loop comprising a group of identical ICs (1, 2, 3), comprising each a first impedance (7) connected in series to the first impedance of another IC of the group. The combination of first impedances is connected to a reference current source (4). The voltage across the first impedance (7) is convened to a current (I0) by a voltage-to-current converter (8) and made available as a current (I1, I2) proportional to the reference current (Iref) of the reference current source (4) by a current mirror circuit (20, 23). The relation between the currents I1 and I2 and the reference current Iref is determined by the ratio of the impedance value of the first impedance (7) to that of the second impedance (19). This ratio is the same for all the ICs, so that the currents I1 and I2 in all the ICs are mutually equal.

I claim: 
     
       1. Reference current loop comprising: a reference current source (4);   a group of at least two integrated circuits (1, 2, 3), each comprising: a first (5) and a second (6) reference current terminal;   a first (7) impedance connected to the first (5) and second (6) reference current terminals;   a second impedance (19) of a similar type to the first impedance (7) and having an impedance value that has a predetermined proportion to the impedance value of the first impedance;   a voltage-to-current converter (8) including: an input (10, 14) for receiving a voltage difference occurring between the first and second reference voltage terminals (5, 6), and an output (24, 25) for supplying an output current (IO) which is a function of the impedance value of the second impedance (19);     a current mirror circuit (20) comprising an input branch (21) and at least one output branch (22), the input branch (21) being coupled to the output (24) of the voltage-to-current converter (8); means for mutually coupling the respective first (5) and second (6) reference current terminals of the integrated circuits (1, 2, 3), the respective first impedances (7) of the integrated circuits forming a series combination and means for coupling the reference current source (4) to the series combination.       
     
     
       2. Reference current loop as claimed in claim 1, characterized in that the voltage-to-current converter (8) comprises: a first and a second operational amplifier (9, 13), having each an inverting input (11, 15), a non-inverting input (10, 14) and an output (12, 16), the non-inverting input (10, 14) of the first and the second operational amplifier (9, 13) respectively, being coupled to the first and the second reference voltage terminal (5, 6) respectively;   a first and a second transistor (17, 18), each comprising control electrode, a first main electrode and a second main electrode, the control electrode of the first and the second transistor (17, 18) respectively, being coupled to the output (12, 16) of the first and second operational amplifier (9, 13) respectively, the first main electrode of the first and the second transistor (17, 18) respectively, being coupled to the inverting input (11, 15) of the first and the second operational amplifier (9, 13) respectively, and the first main electrodes of the first and second transistors being mutually coupled by way of the second impedance (19), the input branch (21) being connected in series to a current path (IO) formed by the first and the second transistor (17, 18) and the second impedance (19).     
     
     
       3. Reference current loop as claimed in claim 1 or 2, characterized in that the first and the second impedances are resistors.